Apparatus for controlling rotary machine

ABSTRACT

In a control apparatus, a filter processor filters target torque for a rotary electric machine to suppress a vibrational frequency component of a drivetrain using a filter having a frequency transfer characteristic. A controller performs drive control of the rotary electric machine according to the filtered target torque. A parameter calculator calculates, according to a running condition of the vehicle, a parameter associated with a request value for responsivity of output torque of the rotary electric machine with respect to the target torque. A variable setter variably sets the frequency transfer characteristic of the filter to decrease a degree of attenuation of the vibrational frequency component with an increase of the request value for responsivity of the actual output torque. A limiter limits a rate of change of the degree of attenuation to suppress vibrations of the drivetrain.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority fromJapanese Patent Application 2014-169111 filed on Aug. 22, 2014, thedisclosure of which is incorporated in its entirety herein by reference.

TECHNICAL FIELD

The present disclosure relates to apparatuses for controlling a rotaryelectric machine that supplies drive power to driving wheels of avehicle via a drivetrain, i.e. a power transmission mechanism.

BACKGROUND

Such control apparatuses include a control apparatus for suppressingvibrational frequency components occurring from the drivetrain, which isfor example disclosed in Japanese Patent Publication No. 5324623. Indetail, the control apparatus, which is installed in a vehicle, filterstarget torque for a motor as an example of rotary electric machines tosuppress such vibrational frequency components contained in the targettorque. Then, the control apparatus controls actual output torque of themotor using the filtered target torque.

SUMMARY

The control of actual output torque of a motor based on the filteredtarget torque may reduce the responsivity of the control as comparedwith the control of actual output torque of the same motor based onunfiltered target torque. The control of actual output torque of themotor with respect to the filtered target torque may therefore cause adisadvantage, such as reduction of the driver's drivability of thevehicle, under some situations where the higher responsivity of thetorque control of the motor should be desired, including a situationwhere the driver wants to make the vehicle maneuver quickly.

In view of the circumstances set forth above, one aspect of the presentdisclosure seeks to provide apparatuses for controlling a rotaryelectric machine, which are capable of addressing such a problem.

Specifically, an alternative aspect of the present disclosure aims toprovide such apparatuses each capable of reducing a disadvantage due tofiltering of target torque to suppress a vibrational frequency componentincluded in the target torque.

According to an exemplary aspect of the present disclosure, there isprovided a control apparatus for a rotary electric machine of a vehicle.The vehicle is equipped with a drivetrain for transmitting power outputfrom the rotary electric machine to driving wheels. The controlapparatus includes a filter processor that filters target torque for therotary electric machine to suppress a vibrational frequency component ofthe drivetrain using a filter having a frequency transfercharacteristic. The control apparatus includes a controller thatperforms drive control of the rotary electric machine according to thefiltered target torque. The control apparatus includes a parametercalculator that calculates, according to a running condition of thevehicle, a parameter associated with a request value for responsivity ofoutput torque of the rotary electric machine with respect to the targettorque. The control apparatus includes a variable setter that variablysets the frequency transfer characteristic of the filter to decrease adegree of attenuation of the vibrational frequency component with anincrease of the request value for responsivity of the actual outputtorque. The control apparatus includes a limiter that limits a rate ofchange of the degree of attenuation to suppress vibrations of thedrivetrain.

The control apparatus according to the exemplary aspect calculates theparameter associated with the request value for responsivity of outputtorque of the rotary electric machine according to the running conditionof the vehicle. That is, the parameter represents how the responsivityof the output torque is set. The control apparatus according to theexemplary aspect variably sets the frequency transfer characteristic ofthe filter to decrease the degree of attenuation of the vibrationalfrequency component with an increase of the request value forresponsivity of the actual output torque.

Reducing the degree of attenuation of the vibrational frequencycomponent with an increase of the request value for responsivity of theactual output torque reduces the delay in phase of the frequencytransfer characteristic. This reduces the response delay of an outputvalue from the filter in response to an input value to the filter. Thismaintains the responsivity of torque control at a higher level to enableimprovement of a driver's drivability of the vehicle in a situationwhere the driver has an intention to make the vehicle maneuver quickly.

In contrast, increasing the degree of attenuation of the vibrationalfrequency component with a decrease of the request value forresponsivity of the actual output torque reduces the responsivity oftorque control at a relatively lower level to increase the effects ofsuppressing vibrations of the drivetrain of the vehicle.

This enables improvement of the driver's comfort in the vehicle.

That is, the control apparatus according to the exemplary aspect adjuststhe responsivity of torque control according to the running condition ofthe vehicle, thus reducing a disadvantage due to filtering of the targettorque for the rotary electric machine.

Additionally, the control apparatus according to the exemplary aspectlimits change of the degree of attenuation to suppress vibrations of thedrivetrain. This reduces vibrational frequency components included inthe target torque due to change of the degree of attenuation, thussuppressing vibrations of the vehicle due to change of the degree ofattenuation.

The above and/or other features, and/or advantages of various aspects ofthe present disclosure will be further appreciated in view of thefollowing description in conjunction with the accompanying drawings.Various aspects of the present disclosure can include and/or excludedifferent features, and/or advantages where applicable. In addition,various aspects of the present disclosure can combine one or morefeature of other embodiments where applicable. The descriptions offeatures, and/or advantages of particular embodiments should not beconstrued as limiting other embodiments or the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects of the present disclosure will become apparent from thefollowing description of embodiments with reference to the accompanyingdrawings in which:

FIG. 1 is a block and structural diagram schematically illustrating anexample of the structure of a control system installed in a vehicleaccording to the first embodiment of the present disclosure;

FIG. 2 is a block diagram schematically illustrating an example of thestructure of a second ECU illustrated in FIG. 1;

FIG. 3A is a graph schematically illustrating how curves of filteredtarget MG torque change over time; the curves correspond to differentvalues of a target attenuation coefficient;

FIG. 3B is a graph schematically illustrating how curves of outputtorque of a drive shaft illustrated in FIG. 1 change over time; thecurves correspond to different values of the target attenuationcoefficient;

FIG. 4A is a graph schematically illustrating how an attenuationparameter according to the first embodiment and that according to arelated technology change over time;

FIG. 4B is a graph schematically illustrating how actual output torqueof a motor-generator illustrated in FIG. 1 according to the firstembodiment and that of the motor-generator according to the relatedtechnology change over time;

FIG. 4C is a graph schematically illustrating how the output torque ofthe drive shaft according to the first embodiment and that according tothe related technology change over time according to the firstembodiment;

FIG. 5 is a block diagram schematically illustrating an example of thestructure of a second ECU according to the second embodiment of thepresent disclosure;

FIG. 6 is a block diagram schematically illustrating an example of thestructure of a second ECU according to the third embodiment of thepresent disclosure;

FIG. 7 is a block and structural diagram schematically illustrating anexample of the structure of a control system installed in a vehicleaccording to the fourth embodiment of the present disclosure;

FIG. 8 is a graph schematically illustrating how each of request torque,target MG torque, and actual output torque of the motor-generatoraccording to the fourth embodiment;

FIG. 9 is a graph schematically illustrating the attenuation parameterstepwisely varies over time as a limited attenuation parameter accordingto a modification of the first embodiment; and

FIG. 10 is a graph schematically illustrating the attenuation parametervaries over time in the form of a first order lag function as thelimited attenuation parameter according to another modification of thefirst embodiment.

DETAILED DESCRIPTION OF EMBODIMENT

The following describes embodiments of the present disclosure withreference to the accompanying drawings. In the embodiments, like partsbetween the embodiments, to which like reference characters areassigned, are omitted or simplified to avoid redundant description.

First Embodiment

The following describes a first embodiment of the present disclosure, towhich an apparatus for controlling a rotary electric machine serving asa main engine of a vehicle VEH is applied, with reference to FIGS. 1 to4.

Referring to FIG. 1, the vehicle VEH includes a motor-generator (MV) 10,an inverter 12, a battery 14, a drive shaft 16, and driving wheels 18.The vehicle VEH also includes a first electronic control unit (ECU) 30and a second ECU 32.

The motor-generator 10 serves as both a motor and a generator; the motorserves as a driving source for running the vehicle VEH. The firstembodiment uses a multiphase rotary machine, particularly, a three-phaserotary machine including three-phase windings (U, V, W-phase windings)as the motor-generator 10. Specifically, the first embodiment is capableof using, for example, a three-phase synchronous motor as themotor-generator 10.

A three-phase voltage-controlled inverter is used as the inverter 12when a three-phase rotary machine is used as the motor-generator 10. Theinverter 12 converts a direct-current (DC) voltage output from thebattery 14 into an alternating-current (AC) voltage, and applies the ACvoltage to the motor-generator 10. This voltage application causes themotor-generator 10 to serve as a motor. In contrast, the motor-generator10 serves as a generator based on driving power received from the driveshaft 16.

The motor-generator 10 has a rotor 10 r and an output shaft 10 a, whichwill be referred to as a motor output shaft 10 a, coupled to the rotor10 r.

To the output shaft 10 a, the driving wheels 18 are coupled via thedrive shaft 16. The first embodiment defines, for example, a drivetrain,which is also called power transmission mechanism or powertrain,including the motor output shaft 10 a and the drive shaft 16.

The vehicle VEH further includes a rotational speed sensor 20. Therotational speed sensor 20 measures a rotational speed of the motoroutput shaft 10 a, i.e. the rotor 10 r, which will be referred to as amotor rotational speed Nm. The measurement value of the rotational speedsensor 20 is input to the second ECU 32. Note that the first embodimentcan provide a sensor in the vehicle VEH; the sensor is capable ofmeasuring an electrical rotational angle or an electrical rotationalangular velocity of the rotor 10 r of the motor-generator 10. In thiscase, the second ECU 32 can calculate the motor rotational speed Nmaccording to the measured electrical rotational angle or electricalangular speed of the rotor 10 r.

The vehicle VEH additionally includes current sensors 34. The currentsensors 34 are operative to measure currents flowing through at leasttwo windings, for example, V- and W-phase windings, in the three-phasewindings of the motor-generator 10 as V- and W-phase currents. Then, thecurrent sensors 34 send the measured V- and W-phase currents to thesecond ECU 32.

Each of the first and second ECUs 30 and 32 is designed as, for example,a microcomputer circuit including essentially, for example, a CPU, amemory unit including a ROM and a RAM, and input/output units. Each ofthe first and second ECUs 30 and 32, i.e. a corresponding CPU, runsvarious programs stored in, for example, the ROM. The first and secondECUs 30 and 32 are configured to communicate information with eachother.

The first ECU 30 is superior in hierarchy to the second ECU 32. That is,the first ECU 30 is, for example, an upstream control unit with respectto the second ECU 32 in the flow of addressing vehicle's user requests.For example, the first ECU 30 supervises overall control of the vehicleVEH. Specifically, the first ECU 30 determines target torque, referredto as target MG torque, Tm* for the motor-generator 10 according tomeasurement signals including, for example,

(1) A user's operated (depressed) quantity, i.e. stroke, Acc of auser-operable accelerator pedal (not shown) of the vehicle VEH, whichwill be referred to as an accelerator operated stroke Acc

(2) A user's operated (depressed) quantity, i.e. stroke, Brk of auser-operable brake pedal (not shown) of the vehicle VEH, which will bereferred to as a brake operated stroke Brk

(3) A running speed V of the vehicle VEH.

In the first embodiment, if the target MG torque Tm* is positive, thecontrol mode of the inverter 12 by the second ECU 32 is set to a powerrunning mode for causing the motor-generator 10 to serve as a motor. Incontrast, if the target MG torque Tm* is negative, the control mode ofthe inverter 12 by the second ECU 32 is set to a regenerative mode forcausing the motor-generator 10 to serve as a generator. In particular,the first ECU 30 of the first embodiment increases a value of the targetMG torque Tm* with an increase of the accelerator operated stroke Acc inthe power running mode.

The brake operated stroke Brk represents a value of driver's requestedbrake torque for slowing down the vehicle VEH. In other words, thesecond ECU 32 calculates a value of the driver's requested brake torquefor slowing down the vehicle VEH according to the brake operated strokeBrk.

In addition, the first ECU 30 outputs the target MG torque Tm* to thesecond ECU 32.

For example, in the first embodiment, an accelerator-pedal sensor 36 isprovided to measure the accelerator operated stroke Acc, and send theaccelerator operated stroke Acc to the first ECU 30. For example, in thefirst embodiment, a brake-pedal sensor 38 is provided to measure thebrake operated stroke Brk, and send the brake operated stroke Brk to thefirst ECU 30. For example, in the first embodiment, a vehicle speedsensor 40 is provided to measure the running speed V of the vehicle VEH,and send the running speed V to the first ECU 30.

The second ECU 32 serves as a control unit for controlling themotor-generator 10. The second ECU 32 receives the target MG torque Tm*,the accelerator operated stroke Acc, the brake operated stroke Brk, andthe running speed V input from the first ECU 30, and receives themeasurement values input from the rotational speed sensor 20.

Then, the second ECU 32 operates, based on the received values, in thepower running mode or the regenerative mode to control on-off operationsof for example, bridge-connected switching elements of the inverter 12.This converts the DC voltage output from the battery 14 into controlledthree-phase AC voltages, thus applying the controlled three-phase ACvoltages to the three-phase windings of the motor-generator 10. Thiscontrols torque of the motor-generator 10 for rotating the rotor 10 r tofollow the target MG torque Tm*.

In particular, in the regenerative mode, the second ECU 32 performs aregenerative control task of the motor-generator 10. The regenerativecontrol task is configured to

(1) Calculate the driver's requested brake torque for slowing down thevehicle VEH according to the brake operated stroke Brk

(2) Satisfy the calculated driver's requested brake torque based on anegative value of output torque of the motor-generator 10 controlled tofollow a negative value of the target MG torque Tm* and brake torquegenerated by a brake system 50 for applying brake force to each wheel ofthe vehicle VEH to slow down the vehicle VEH.

The negative value of the output torque of the motor-generator 10, whichwill also be referred to as regenerative torque of the motor-generator10, serves the motor-generator 10 as a generator to generate ACelectrical energy, i.e. regenerative power, based on kinetic energy ofthe driving wheels 18 of the vehicle VEH. The generated AC electricalenergy is converted into DC electrical energy by the inverter 12, andthe DC electrical energy is charged into the battery 14.

The second ECU 32 of the first embodiment shifts its operating mode tothe regenerative mode from the power running mode to perform theregenerative control task of the motor-generator 10 on the conditionsthat

(1) The running speed V is equal to or higher than a predeterminedthreshold speed zero predetermined to be higher than zero

(2) The driver is not operating the accelerator pedal

(3) The driver is operating the brake pedal.

The second ECU 32 is capable of determining whether the driver is notoperating the accelerator pedal according to the accelerator operatedstroke Acc, and determining whether the driver is operating the brakepedal according to the brake operated stroke Brk.

The second ECU 32 operates in the regenerative mode under one of thefollowing conditions:

(1) The vehicle VEH is slowing down while the driver is operating thebrake pedal

(2) The vehicle VEH is running downhill while the running speed V ismaintained at a predetermined speed with the brake pedal being operatedby the driver.

In the regenerative mode, the second ECU 32 can calculate the vehiclespeed V according to the motor rotational speed Nm.

Next, the following describes an example of the specific structure ofthe second ECU 32 for performing torque control of the motor-generator10 based on the target MG torque Tm* with reference to the block diagramof FIG. 2.

As illustrated in FIG. 2, the second ECU 32 includes a calculator 32 a,a limiter 32 b, a target attenuation-coefficient setter 32 c, a filterprocessor 32 d, and a drive controller 32 d 1. These elements 32 a to 32d 1 can be implemented in the second ECU 32 as hardware elements,software elements, and/or hardware-software hybrid elements.

These elements 32 a to 32 d 1 are configured to suppress resonance ofthe drivetrain when, for example, the target MG torque Tm* rapidlychanges, thus suppressing vibrations of the vehicle VEH. Resonance ofthe drivetrain occurs due to, for example, resonant frequency componentsof the drivetrain contained in the target MG torque Tm* when, forexample, the target MG torque Tm* suddenly changes. For example, theresonance of the drivetrain can be expressed as a known torsionalvibration model, more specifically as a known first harmonic drivetraintorsional vibration model.

Specifically, the torsional vibration model of the drivetrain iscomprised of a model including the moment of inertia of themotor-generator 10 and the equivalent mass moment of inertia of thevehicle VEH linked together via a torsional spring. The resonantfrequency frz of the drivetrain is variably set within, for example, therange from 2 to 10 Hz inclusive.

The calculator 32 a calculates, according to running conditions of thevehicle VEH including the accelerator operated stroke Acc, the brakeoperated stroke Brk, and/or the running speed V, an attenuationparameter Atp. The attenuation parameter Atp serves as a parameterassociated with a request value for the responsivity of the actualoutput torque Tm of the motor-generator 10 with respect to the target MGtorque Tm*; the responsivity will be referred to as a torqueresponsivity of the motor-generator 10. The attenuation parameter Atpalso serves as a parameter for determining how vibrational frequencycomponents are attenuated.

Specifically, the calculator 32 a calculates the attenuation parameterAtp such that the attenuation parameter Atp decreases with an increaseof the request value for the torque responsivity of the motor-generator10.

In particular, the calculator 32 a reduces the attenuation parameter Atpwith an increase of change of the accelerator operated stroke Acc perunit time. In other words, the calculator 32 a adjusts the attenuationparameter Atp such that a value of the attenuation parameter Atp for afirst case is smaller than a value of the attenuation parameter Atp fora second case. The first case represents a case where an increase of theaccelerator operated stroke Acc per unit time is greater than apredetermined threshold change, i.e. a predetermined threshold increase,of the accelerator operated stroke Acc per unit time. The second caserepresents a case where an increase of the accelerator operated strokeAcc per unit time is equal to or smaller than the predeterminedthreshold increase, of the accelerator operated stroke Acc per unittime.

Additionally, the calculator 32 a reduces a value of the attenuationparameter Atp during execution of the regenerative control task to besmaller than a value of the attenuation parameter Atp while theregenerative control task is not being executed. The calculator 32 a candetermine whether the second ECU 32 is carrying out the regenerativecontrol task according to the accelerator operated stroke Acc, the brakeoperated stroke Brk, and the running speed V.

Specifically, the calculator 32 a is capable of determining, accordingto the accelerator operated stroke Acc, the brake operated stroke Brk,and/or the running speed V,

(1) Whether the driver has an intention to make the vehicle VEHaccelerate

(2) Whether the regenerative control task is being performed.

The limiter 32 b applies a limiting task to the attenuation parameterAtp, and outputs a limited attenuation parameter Attr to which thelimiting task has been applied. The limiting task will be describedlater.

The target attenuation-coefficient setter 32 c variably sets a targetattenuation-coefficient ξ_(tag), which represents a target value of thedegree of attenuation of the vibrational frequency components, accordingto the limited attenuation parameter Attr. For example, the targetattenuation-coefficient setter 32 c of the first embodiment can haverelational information RI, such as a two-dimensional map illustrated inFIG. 2 or an equation, in which values of the targetattenuation-coefficient ξ_(tag) correlating with corresponding values ofthe limited attenuation parameter Attr are included. In FIG. 2, therelational information RI represents that the targetattenuation-coefficient ξ_(tag) is a linear function of the limitedattenuation parameter Attr with a positive gradient.

In this case, the target attenuation-coefficient setter 32 c refers tothe relational information RI using a value of the limited attenuationparameter Attr as input data to read a value of the targetattenuation-coefficient ξ_(tag) corresponding to the input data value ofthe limited attenuation parameter Attr. Then, the targetattenuation-coefficient setter 32 c outputs the value of the targetattenuation-coefficient ξ_(tag) to the filter processor 32 d.

For example, the target attenuation-coefficient setter 32 c increasesthe target attenuation-coefficient ξ_(tag) with an increase of thelimited attenuation parameter Attr. In particular, the targetattenuation-coefficient setter 32 c of the first embodiment sets thetarget attenuation-coefficient ξ_(tag) to a prescribedattenuation-coefficient ξ_(p) when the limited attenuation parameterAttr becomes its minimum value Attmin, and to 1 when the limitedattenuation parameter Attr becomes its maximum value Attmax. Note thatthe attenuation-coefficient ξ_(p) is previously set to be a value morethan zero and less than 1.

The filter processor 32 d filters the target MG torque Tm* based on afilter having predetermined filter transfer characteristics I(s) whileadjusting the filter transfer characteristics I(s) according to thetarget attenuation-coefficient ξ_(tag) output from the targetattenuation-coefficient setter 32 c; s represents Laplace operator.

Let us describe the filter transfer characteristics I(s) according tothe first embodiment.

First, let us develop frequency transfer characteristics of a vehicleplant model having torque output from the motor-generator 10 to themotor output shaft 10 a as its input, and output torque Tds of the driveshaft 16 as its output. The frequency transfer characteristics will alsobe referred to as modeled transfer characteristics Gpm(s). The firstembodiment expresses the equations of motion of a vehicle by thefollowing equations [eq1] to [eq6]:

$\begin{matrix}{{{J_{m} \cdot \frac{\mathbb{d}}{\mathbb{d}t}}\omega_{m}} = {T_{m} - \frac{T_{ds}}{N_{al}}}} & \lbrack {{eq}\mspace{14mu} 1} \rbrack \\{{2\;{J_{w} \cdot \frac{\mathbb{d}}{\mathbb{d}t}}\omega_{w}} = {T_{ds} - {r \cdot F}}} & \lbrack {{eq}\mspace{14mu} 2} \rbrack \\{{{M_{c} \cdot \frac{\mathbb{d}}{\mathbb{d}t}}V_{c}} = F} & \lbrack {{eq}\mspace{14mu} 3} \rbrack \\{T_{ds} = {K_{d} \cdot \theta}} & \lbrack {{eq}\mspace{14mu} 4} \rbrack \\{F = {K_{t}( {{r \cdot \omega_{m}} - V_{c}} )}} & \lbrack {{eq}\mspace{14mu} 5} \rbrack \\{\theta = {\int{( {\frac{\omega_{m}}{N_{al}} - \omega_{w}} ){\mathbb{d}t}}}} & \lbrack {{eq}\mspace{14mu} 6} \rbrack\end{matrix}$

Where:

J_(m) represents the inertia of the rotor 10 r of the motor-generator 10

J_(w) represents the inertia of the driving wheels 18

ω_(m) represents the angular frequency of the rotor 10 r of themotor-generator 10

ω_(w) represents the angular frequency of the driving wheels 18

T_(m) represents output torque of the motor-generator 10

T_(ds) represents actual output torque of the driving wheels 18, i.e.the drive shaft 16

N_(al) represents an overall gear ratio of the vehicle VEH

K_(d) represents torsional rigidity of the drivetrain, i.e. the driveshaft 16

r represents a dynamic loaded radius of each wheel of the vehicle VEH

F represents drive power of the vehicle VEH

M_(c) represents the mass of the vehicle VEH

V_(c) represents the running speed of the vehicle VEH

θ represents a twisting angle of the drive shaft 16.

Performing Laplace transform of these equations [eq1] to [eq6] resultsin expression of the modeled transfer characteristics Gpm(s) by thefollowing equation [eq7]:

$\begin{matrix}{{{Gpm}(s)} = {\frac{T_{ds}}{T_{m}} = {\frac{K_{d}( {{p_{1} \cdot s} + p_{0}} )}{{a_{3} \cdot s^{3}} + {a_{2} \cdot s^{2}} + {a_{1} \cdot s} + a_{0}} = \frac{K_{d}( {{p_{1} \cdot s} + p_{0}} )}{{a_{3}( {s + \alpha} )}( {s^{2} + {2\;{\xi_{p} \cdot \omega_{p} \cdot s}} + \omega_{p}^{2}} )}}}} & \lbrack {{eq}\mspace{14mu} 7} \rbrack\end{matrix}$

Where

$p_{1} = {\cdot \frac{2\;{J_{m} \cdot M_{c}}}{N_{al}}}$$p_{0} = \frac{K_{t}( {{2\; J_{w}} + {r^{2} \cdot M_{c}}} )}{N_{al}}$a₃ = 2 J_(m) ⋅ J_(w) ⋅ M_(c) a₂ = K_(t) ⋅ J_(m)(2 J_(w) + r² ⋅ M_(c))$a_{1} = {K_{d} \cdot {M_{c}( {J_{m} + \frac{2\; J_{W}}{N_{al}^{2}}} )}}$$a_{0} = {K_{d} \cdot {K_{t}( {J_{m} + \frac{2\; J_{w}}{N_{al}^{2}} + \frac{r^{2} \cdot M_{c}}{N_{al}^{2}}} )}}$

In the equation [eq7], reference character s represents the Laplaceoperator, and reference character ξ_(p) of the second-order lag elementrepresents the prescribed attenuation coefficient, which is anattenuation coefficient for the drivetrain. In the equation [eq7],reference character ωp of the second-order lag element represents aresonant angular frequency, i.e. a natural angular frequency, of thedrivetrain. The first embodiment respectively sets the resonant angularfrequency ωp and the prescribed attenuation coefficient ξ_(p) to fixedvalues. The reason why the modeled transfer characteristics Gpm(s) areexpressed by the equation [eq7] is that actual frequency transfercharacteristics Gpr(s) of the drivetrain, to which reference character40 is assigned, is approximated by the equation [eq7].

Next, let us express target frequency transfer characteristics of atarget vehicle plant model, which has torque output from themotor-generator 10 to the motor output shaft 10 a as an input, andoutput torque Tds of the drive shaft 16 as an output, by the followingequation [eq8]:

$\begin{matrix}{{{Gr}(s)} = \frac{K_{d}( {{p_{1} \cdot s} + p_{0}} )}{{a_{3}( {s + \alpha} )}( {s^{2} + {2\;{\xi_{tag} \cdot \omega_{p} \cdot s}} + \omega_{p}^{2}} )}} & \lbrack {{eq}\mspace{14mu} 8} \rbrack\end{matrix}$

Where Gr(s) represents the target frequency transfer characteristics ofthe target vehicle plant model.

Replacing the prescribed attenuation coefficient ξ_(p) described in theequation [eq7] with the target attenuation coefficient ξ_(tag) obtainsthe equation [eq8].

From the equations [eq7] and [eq8], the following equation [eq9], whichexpresses the filter transfer characteristics I(s), is derived asfollows:

$\begin{matrix}{{I(s)} = {\frac{{Gr}(s)}{{Gpm}(s)} = \frac{s^{2} + {2\;{\xi_{p} \cdot \omega_{p} \cdot s}} + \omega_{p}^{2}}{s^{2} + {2\;{\xi_{tag} \cdot \omega_{p} \cdot s}} + \omega_{p}^{2}}}} & \lbrack {{eq}\mspace{14mu} 9} \rbrack\end{matrix}$

The dimension of the target frequency transfer characteristics, referredto as target transfer characteristics, Gr(s) and that of the modeledtransfer characteristic Gpm(s) are identical to each other, resulting inthe filter transfer characteristics I(s) being non-dimensionalcharacteristics. The inverse of the modeled transfer characteristicGpm(s) in the filter transfer characteristics I(s) serves as an inversefilter for suppressing resonance of the drivetrain.

Specifically, the filter processor 32 d is configured to filter thetarget MG torque Tm* based on the filter transfer characteristics I(s)expressed in the equation [eq9].

This configuration sets the target attenuation coefficient ξ_(tag) tothe prescribed attenuation coefficient ξ_(p) when the limitedattenuation parameter Attr becomes its minimum value Attmin. Thissetting causes the filter transfer characteristics I(s) to be 1,resulting in the target MG torque Tm*, which is input to the filterprocessor 32 d, being output from the filter processor 32 d as it is.

In contrast, the configuration sets the target attenuation coefficientξ_(tag) to 1 when the limited attenuation parameter Attr becomes itsmaximum value Attmax, resulting in the target MG torque Tm*, which isinput to the filter processor 32 d, being output from the filterprocessor 32 d while being attenuated.

FIG. 2 schematically illustrates the target MG torque Tm* output fromthe filter processor 32 d as filtered target MG torque, i.e. filteredtarget MG torque, Tam*.

FIG. 3A schematically illustrates how curves of the filtered target MGtorque Tam* change over time; the curves are obtained when correspondingvalues of the target attenuation coefficient ξ_(tag) are set todifferent values within the range from 1 to the prescribed attenuationcoefficient ξ_(p). FIG. 3B also schematically illustrates how curves ofthe output torque Tds of the drive shaft 16 change over time; the curvesare obtained when corresponding values of the target attenuationcoefficient ξ_(tag) are set to different values within the range from 1to the prescribed attenuation coefficient ξ_(p).

For example, each of FIGS. 3A and 3B shows the curve, which is obtainedwhen the corresponding target attenuation coefficient ξ_(tag) is set tothe prescribed attenuation coefficient ξ_(p), drawn by a solid line.Similarly, each of FIGS. 3A and 3B shows the curve, which is obtainedwhen the target attenuation coefficient ξ_(tag) is set to 1, drawn by asolid line.

In addition, each of FIGS. 3A and 3B shows the curves, which areobtained when corresponding three different values are assigned to thetarget attenuation coefficient ξ_(tag), drawn by respective dashed,dot-and-dash, and two-dot chain lines. The dashed, dot-and-dash, andtwo-dot chain curves have a characteristic that the corresponding valuesof the target attenuation coefficient ξ_(tag) increase in the order fromthe dashed curve, the dot-and-dash curve, to the two-dot chain curve.

FIGS. 3A and 3B show that the target MG torque Tm* steeply rises in astep function at time t1, and after the time t1, show that, the smallerthe value of the target attenuation coefficient ξ_(tag) is, the more theresponsivity of torque control is improved.

In particular, the filter processor 32 d can convert the filter transfercharacteristics I(s) represented in a complex domain, i.e. S domain,into, for example, discretized filter transfer characteristics I(z) in adiscretized complex domain, i.e. Z domain. Then, the filter processor 32d can perform filtering of the target MG torque Tm* using thediscretized filter transfer characteristics I(z).

The drive controller 32 d 1 performs on-off control of thebridge-connected switching elements of the inverter 12 according to thefiltered target MG torque Tm* to convert the DC voltage output from thebattery 14 into a controlled AC voltage, thus applying the controlled ACvoltage to the three-phase windings of the motor-generator 10. Thiscauses output torque of the motor-generator 10 to follow the filteredtarget MG torque Tam*. The drive controller 32 d 1 can perform knowncurrent vector control as an example of the on-off control of theswitching elements of the inverter 12.

For example, the current vector control calculates, from the measured V-and W-phase currents, the remaining phase, i.e. the U-phase, current,and converts the three-phase currents (U-, V-, and W-phase currents)into a current value in a first axis and a current value in a secondaxis; the first axis and second axis define a rotating Cartesiancoordinate system in the rotor 10 r. The rotating Cartesian coordinatesystem rotates as the rotor 10 r rotates. The current vector controlobtains a first deviation between the first-axis measured current valueand a first-axis command current, and a second deviation between thesecond-axis measured current value and a second-axis command current.Then, the current vector control obtains three-phase AC command voltagesthat should zero the first and second deviations. The current vectorcontrol controls on-off operations of the switching elements of theinverter 12 according to the obtained three-phase command voltages, thuscausing output torque of the motor-generator 10 to follow the filteredtarget MG torque Tam*.

As described above, the second ECU 32, which serves as a component of acontrol apparatus for the motor-generator 10, calculates, according tothe accelerator operated stroke Acc, the brake operated stroke Brk, andthe running speed V, an attenuation parameter Atp. The attenuationparameter Atp serves as a parameter associated with a request value forthe torque responsivity of the motor-generator 10. The attenuationparameter Atp also serves as a parameter for determining how vibrationalfrequency components are attenuated.

In particular, the second ECU 32 determines whether the driver has anintention to make the vehicle VEH maneuver quickly according to, forexample, an increase of change of the accelerator operated stroke Accper unit time. Then, the second ECU 32 reduces a value of theattenuation parameter Atp for a case where the driver has an intentionto make the vehicle VEH maneuver quickly to be smaller than a value ofthe attenuation parameter Atp for a case where the driver has nointention to make the vehicle VEH maneuver quickly.

Additionally, the second ECU 32 determines whether the regenerativecontrol task is being performed according to, for example, theaccelerator operated stroke Acc, the brake operated stroke Brk, and/orthe running speed V. Then, the second ECU 32 reduces a value of theattenuation parameter Atp for a case where the regenerative control taskis being performed to be smaller than a value of the attenuationparameter Atp for a case where no regenerative control task is beingperformed.

The reduction in the value of the attenuation parameter Atp reduces thetarget attenuation coefficient ξ_(tag), thus improving the responsivityof the torque control (see FIGS. 3A and 3B).

Specifically, this configuration of the second ECU 32 reduces the delayin phase of the filter transfer characteristics I(s) of the filter, thusreducing the response delay of an output value from the filter inresponse to an input value to the filter; This

This configuration of the second ECU 32 therefore enables bothimprovement of the driver's drivability of the vehicle VEH andadjustment of regenerative torque of the motor-generator 10 toimmediately follow the target MG torque Tm* in the regenerative modewhile suppressing vibrations of the drivetrain of the vehicle VEH.

On the other hand, the second ECU 32 increases a value of theattenuation parameter Atp for a case where the driver has an intentionto run the vehicle VEH with a higher degree of comfort to be larger thana value of the attenuation parameter Atp for a case where the driver hasan intention to make the vehicle VEH maneuver quickly.

The increase in the value of the attenuation parameter Atp increases thetarget attenuation coefficient ξ_(tag), thus increasing the degree ofattenuation of the target MG torque Tm* (FIGS. 3A and 3B).

Specifically, this configuration of the second ECU 32 enablesimprovement of the driver's comfortability of the vehicle VEH whileimproving the effects of suppressing vibrations of the drivetrain of thevehicle VEH.

Rapid change of the attenuation parameter Atp while the filtered targetMG torque Tam* is changing may cause resonant frequency components ofthe drivetrain to be contained in the filtered target MG torque Tam*.The resonant frequency components might cause the vehicle VEH tovibrate.

In order to address such vibrations of the vehicle VEH due to steepchange of the attenuation parameter Atp, the second ECU 32 is comprisedof the limiter 32 b.

The limiter 32 b applies the limiting task to the attenuation parameterAtp to limit the rate of change of the attenuation parameter Atp. Inother words, the limiter 32 b gradually changes the attenuationparameter Atp to reduce the rate of change of the attenuation parameterAtp. In particular, the limiter 32 b gradually changes the attenuationparameter Atp in the form of a linear function while having theinclination, i.e. the gradient, of the linear function gentler than theinclination, i.e. the gradient, of change of the attenuation parameterAtp.

FIGS. 4A to 4C illustrate results of the torque control including thelimiting task as compared with results of the torque control withoutincluding the limiting task.

In detail, a solid line of FIG. 4A schematically illustrates how each ofthe attenuation parameter Atp and the limited attenuation parameter Attrchanges over time according to the first embodiment. A dashed line ofFIG. 4A schematically illustrates how the attenuation parameter Atpchanges over time according to a related technology. The relatedtechnology is configured such that the attenuation parameter Atp isdirectly input to the target attenuation-coefficient setter 32 c inplace of the limited attenuation parameter Attr, thus setting the targetattenuation coefficient ξ_(tag) using the attenuation parameter Atp asit is.

A solid line of FIG. 4B schematically illustrates how the actual outputtorque Tm of the motor-generator 10 changes over time according to thefirst embodiment, and a dashed line of FIG. 4B schematically illustrateshow the actual output torque Tm of the motor-generator 10 changes overtime according to the related technology. A dot-and-dash line of FIG. 4Billustrates the target MG torque Tm* of the motor-generator 10 accordingto each of the first embodiment and the related technology.

A solid line of FIG. 4C schematically illustrates how the output torqueTds of the drive shaft 16 changes over time according to the firstembodiment. A dashed line of FIG. 4C schematically illustrates how theoutput torque Tds of the drive shaft 16 changes over time according tothe related technology.

FIGS. 4A to 4C demonstrate that, in the related technology, after asteep change of the target MG torque Tm* at time t10, the attenuationparameter Atp rapidly falls at time t2.

In contrast, FIGS. 4A to 4C demonstrate that the limiter 32 b limits therate of change of the attenuation parameter Atp, in other words,gradually changes the attenuation parameter Atp to reduce the rate ofchange of the attenuation parameter Atp.

Thus, the second ECU 32 of the first embodiment efficiently suppressesvibrations of the vehicle VEH due to steep change of the attenuationparameter Atp.

Second Embodiment

The following describes a second embodiment of the present disclosurewith reference to FIG. 5 while focusing on the different points betweenthe second embodiment and the first embodiment.

Referring to FIG. 5, a second ECU 32A of the second embodiment includesa target attenuation-coefficient setter 32 e and a filter processor 32f, which differ from the target attenuation-coefficient setter 32 c andfilter processor 32 d, in addition to the components 32 a, 32 b, and 32e.

For example, the target attenuation-coefficient setter 32 e of thesecond embodiment can have relational information RIA, such as atwo-dimensional map illustrated in FIG. 5 or an equation, in whichvalues of the target attenuation-coefficient ξ_(tag) correlating withcorresponding values of the limited attenuation parameter Attr areincluded. In FIG. 5, the relational information RIA represents that thetarget attenuation-coefficient ξ_(tag) is a linear function of thelimited attenuation parameter Attr with a negative gradient.

Specifically, the target attenuation-coefficient setter 32 e reduces thetarget attenuation-coefficient ξ_(tag) with an increase of the limitedattenuation parameter Attr. In particular, the targetattenuation-coefficient setter 32 e sets the targetattenuation-coefficient ξ_(tag) to 1 when the limited attenuationparameter Attr becomes its minimum value Attmin, and to the prescribedattenuation-coefficient ξ_(p) when the limited attenuation parameterAttr becomes its maximum value Attmax.

The filter processor 32 f filters the target MG torque Tm* output fromthe target attenuation-coefficient setter 32 c based on predeterminedfilter transfer characteristics I(s) while adjusting the filter transfercharacteristics I(s) according to the target attenuation-coefficientξ_(tag) output from the target attenuation-coefficient setter 32 e. Thesecond embodiment expresses modeled transfer characteristics Gpm(s) bythe following equation [eq10]:

$\begin{matrix}{{{Gpm}(s)} = \frac{K_{d}( {{p_{1} \cdot s} + p_{0}} )}{{a_{3}( {s + \alpha} )}( {s^{2} + {2\;{\xi_{tag} \cdot \omega_{p} \cdot s}} + \omega_{p}^{2}} )}} & \lbrack {{eq}\mspace{14mu} 10} \rbrack\end{matrix}$

Replacing the prescribed attenuation coefficient ξ_(p) in the equation[eq7] with the target attenuation-coefficient ξ_(tag) establishes theequation [eq10].

The second embodiment also expresses target transfer characteristicsGr(s) by the following equation [eq11]:

$\begin{matrix}{{{Gr}(s)} = \frac{K_{d}( {{p_{1} \cdot s} + p_{0}} )}{{a_{3}( {s + \alpha} )}( {s^{2} + {2\;{\omega_{p} \cdot s}} + \omega_{p}^{2}} )}} & \lbrack {{eq}\mspace{14mu} 11} \rbrack\end{matrix}$

Replacing the target attenuation-coefficient ξ_(tag) in the equation[eq8] with 1 establishes the equation [eq11].

From the equations [eq10] and [eq11], the following equation [eq12],which expresses the filter transfer characteristics I(s) is derived asfollows:

$\begin{matrix}{{I(s)} = {\frac{{Gpr}(s)}{{Gpm}(s)} = \frac{s^{2} + {2\;{\xi_{tag} \cdot \omega_{p} \cdot s}} + \omega_{p}^{2}}{s^{2} + {2\;{\omega_{p} \cdot s}} + \omega_{p}^{2}}}} & \lbrack {{eq}\mspace{14mu} 12} \rbrack\end{matrix}$

This configuration of the second ECU 32A of the second embodiment setsthe target attenuation-coefficient ξ_(tag) to 1 when the limitedattenuation parameter Attr becomes its minimum value Attmin, resultingin the filter transfer characteristics I(s) being 1. On the other hand,this configuration of the second ECU 32A sets the targetattenuation-coefficient ξ_(tag) to the prescribed attenuationcoefficient when the limited attenuation parameter Attr becomes itsmaximum value Attmax.

The limiter 32 b of the second ECU 32A of the second embodimentefficiently suppresses vibrations of the vehicle VEH due to steep changeof the attenuation parameter Atp. This therefore achieves substantiallythe same effects as those achieved by the first embodiment.

Third Embodiment

The following describes a third embodiment of the present disclosurewith reference to FIG. 6 while focusing on the different points betweenthe third embodiment and the first embodiment.

A second ECU 32B of the third embodiment includes a limiter 32 gprovided between the target attenuation-coefficient setter 32 c and thefilter processor 32 d, and the limiter 32 b is eliminated. The secondembodiment represents an attenuation parameter output from thecalculator 32 a as the attenuation parameter Attr.

Like the first embodiment, the target attenuation-coefficient setter 32c variably sets the target attenuation-coefficient ξ_(tag) according tothe attenuation parameter Attr output from the calculator 32 a.

The target attenuation-coefficient ξ_(tag) output from the targetattenuation-coefficient setter 32 c is input to the limiter 32 g.

The limiter 32 g applies a limiting task to the targetattenuation-coefficient ξ_(tag) to limit the rate of change of thetarget attenuation-coefficient ξ_(tag). In other words, the limiter 32 ggradually changes the target attenuation-coefficient ξ_(tag) to reducethe rate of change of the target attenuation-coefficient ξ_(tag). Inparticular, the limiter 32 g gradually changes the targetattenuation-coefficient ξ_(tag) in the form of a linear function whilehaving an inclination of the linear function gentler than theinclination of change of the target attenuation-coefficient ξ_(tag).

A target attenuation-coefficient, to which the limiting task has beenapplied, will be referred to as a target attenuation-coefficient ξfhereinafter. The target attenuation-coefficient 4 f is input to thefilter processor 32 d.

The filter processor 32 d filters the target MG torque Tm* output fromthe target attenuation-coefficient setter 32 c based on the filtertransfer characteristics I(s) while adjusting the filter transfercharacteristics I(s) according to the target attenuation-coefficientξ_(f) output from the target attenuation-coefficient setter 32 c; thefilter transfer characteristics I(s) is expressed by the followingequation [eq13]:

$\begin{matrix}{{I(s)} = \frac{s^{2} + {2\;{\xi_{p} \cdot \omega_{p} \cdot s}} + \omega_{p}^{2}}{s^{2} + {2\;{\xi_{f} \cdot \omega_{p} \cdot s}} + \omega_{p}^{2}}} & \lbrack {{eq}\mspace{14mu} 13} \rbrack\end{matrix}$

The limiter 32 g of the third ECU 32B of the third embodimentefficiently suppresses vibrations of the vehicle VEH due to steep changeof the target attenuation-coefficient ξ_(tag). This therefore achievessubstantially the same effects as those achieved by the firstembodiment.

Fourth Embodiment

The following describes a fourth embodiment of the present disclosure,to which an apparatus for controlling a rotary electric machineinstalled in a vehicle VEH1 is applied, with reference to FIGS. 7 and 8while focusing on the different points between the fourth embodiment andthe first embodiment.

Referring to FIG. 7, the vehicle VEH1 further includes a known internalcombustion engine, referred to as an engine, 22 as a main engine of thevehicle VEH1 in addition to the motor-generator 10. The vehicle VEH1also includes a power splitter 24 and a third ECU 34.

The engine 22 has a crankshaft 22 a coupled to the power splitter 24. Tothe power splitter 24, the motor output shaft 10 a is also coupled.

The power splitter 24 is also coupled to the drive shaft 16. Forexample, the power splitter 24 is configured to transfer power suppliedfrom at least one of the engine 22 and the motor-generator 10 to thedrive shaft 16, and split power supplied from the engine 22 to transferthe first split power to the drive shaft 16 and the second split powerto the motor-generator 10. For example, the power splitter 24 is alsoconfigured to freely integrate power supplied from the motor-generator10 and power supplied from the engine 22, and transfer the integratedpower to the drive shaft 16. The drivetrain of the fourth embodimentincludes, for example, the motor output shaft 10 a, the crankshaft 22 a,the power splitter 24, and the drive shaft 16.

The third ECU 34 is designed as, for example, a microcomputer circuitincluding essentially, for example, a CPU, a memory unit including a ROMand a RAM, and input/output units. The third ECU 34, i.e. acorresponding CPU, runs various programs stored in, for example, theROM. The first ECU 30, a second ECU 32C, and the third ECU 34 areconfigured to communicate information with each other.

The first ECU 30 is superior in hierarchy to each of the second andthird ECUs 32 and 34. That is, the first ECU 30 is, for example, anupstream control unit with respect to the second and third ECUs 32 and34 in the flow of addressing vehicle's user requests. The first ECU 30calculates request torque Tall of the vehicle VEH1 according to, forexample, the accelerator operated stroke Acc. Then, the first ECU 30splits the request torque Tall into target MG torque Tm* and targettorque of the engine 22, which will be referred to as target enginetorque Te*. Then, the first ECU 30 outputs the target MG torque Tm*allocated for the motor-generator 10 to the second ECU 32, and thetarget engine torque Te* allocated for the engine 22 to the third ECU34. Note that the fourth embodiment for example assumes that the targetengine torque Te* is set to be equal to or more than zero.

The third ECU 34 serves as a control unit for controlling the engine 22.The third ECU 34 receives at least the target engine torque Te* inputfrom the first ECU 30. The third ECU 34 controls, based on the receivedtarget engine torque Te*, the proper quantity of fuel to be sprayed froman injector provided for each cylinder of the engine 22 into thecombustion chamber of the corresponding cylinder, and proper ignitiontiming for an igniter provided for each cylinder of the engine 22. Thiscontrol of the engine 22 controls actual torque generated from theengine 22 to follow the target engine torque Te*.

The calculator 32 a of the second ECU 32C adjusts the attenuationparameter Atp such that a value of the attenuation parameter Atp for afirst situation is greater than a value of the attenuation parameter Atpfor a second situation. The first situation represents a situation whereeach of the target MG torque Tm* and the target engine torque Te* ismore than zero and the request torque Tall of the vehicle VEH1 istransiently increasing (see the period from time t11 to time t12 of FIG.8). The second situation represents a situation where the request torqueTall of the vehicle VEH1 is in a steady state (see the period after thetime t12 of FIG. 8). The situation where each of the target MG torqueTm* and the target engine torque Te* is more than zero shows that poweroutput from each of the motor-generator 10 and the engine 22 is beingtransferred to the driving wheels 18.

The torque responsivity of the motor-generator 10 is higher than thetorque responsivity of the engine 22. This brings the output torque Tmof the motor-generator 10 to have a dominant influence on the integratedoutput torque of the motor-generator 10 and the engine 22 while therequest torque Tall of the vehicle VEH1 is transiently changing, i.e. istransiently increasing (accelerating). Thus, the second ECU 32Cincreases a value of the attenuation parameter Atp while the requesttorque Tall of the vehicle VEH1 is transiently changing as compared witha value of the attenuation parameter Atp while the request torque Tallof the vehicle VEH1 is in a steady state. This performs suppressingvibrations of the drivetrain of the vehicle VEH by the filter processor32 d prior to improvement of the driver's drivability of the vehicleVEH1.

In contrast, the second ECU 32C decreases a value of the attenuationparameter Atp while the request torque Tall of the vehicle VEH1 is in asteady state as compared with a value of the attenuation parameter Atpwhile the request torque Tall of the vehicle VEH1 is transientlychanging. This performs adjustment of the actual output torque Tm of themotor-generator 10 to follow the target MG torque Tm* with a higherresponsivity prior to suppression of the vibrations of the vehicle VEH1.This therefore results in adjustment of the integrated torque of themotor-generator 10 and the engine 22 to immediately follow the requesttorque Tall of the vehicle VEH1, thus immediately satisfying thedriver's acceleration request. This therefore improves the driver'sdrivability of the vehicle VEH1.

Each of the first to fourth embodiments can be modified as follows.

The limiter 32 b of the first embodiment performs the limiting task togradually and continuously change the attenuation parameter Atp as thelimited attenuation parameter Attr over time, but the present disclosureis not limited thereto. Specifically, the limiter 32 b of the presentdisclosure can perform a modified limiting task to gradually andstepwisely change the attenuation parameter Atp over time (see FIG. 9).

The limiter 32 b of the first embodiment gradually changes theattenuation parameter Atp in the form of a linear function as thelimited attenuation parameter Attr, but can gradually change theattenuation parameter Atp in the form of an N-th order lag function asthe limited attenuation parameter Attr; N is an integer equal to or morethan 1. FIG. 10 schematically illustrates that the attenuation parameterAtp is changed in the form of a first order lag function as the limitedattenuation parameter Attr.

The second embodiment can be modified to eliminate the limiter 32 b, andprovide a limiter 32 g between the target attenuation-coefficient setter32 c and the filter processor 32 d like the third embodiment.

The limiter 32 b can determine whether the rate, i.e. inclination, ofchange of the attenuation parameter Atp, in other words, the absoluteamount of change of the attenuation parameter Atp per unit time, isequal to or higher than a predetermined first threshold rate, i.e.inclination.

Upon determination that the rate of change of the attenuation parameterAtp is equal to or higher than the predetermined first threshold rate ofchange, the limiter 32 b applies the limiting task to the attenuationparameter Atp to limit the rate of change of the attenuation parameterAtp.

Otherwise, upon determination that the rate of change of the attenuationparameter Atp is lower than the predetermined first threshold rate ofchange, the limiter 32 b does not apply the limiting task to theattenuation parameter Atp, thus outputting the attenuation parameter Atpas it is.

This configuration more efficiently balances between the improvement ofsuppressing vibrations of the drivetrain of the vehicle VEH and theimprovement of the driver's drivability of the vehicle VEH.

Similarly, the limiter 32 g can determine whether the rate, i.e.inclination, of change of the target attenuation-coefficient ξ_(tag), inother words, the absolute amount of change of the targetattenuation-coefficient ξ_(tag) per unit time, is equal to or higherthan a predetermined second threshold rate, i.e. inclination.

Upon determination that the rate of change of the targetattenuation-coefficient ξ_(tag) is equal to or higher than thepredetermined second threshold rate of change, the limiter 32 g appliesthe limiting task to the target attenuation-coefficient ξ_(tag) to limitthe rate of change of the target attenuation-coefficient ξ_(tag).

Otherwise, upon determination that the rate of change of the targetattenuation-coefficient ξ_(tag) is lower than the predetermined secondthreshold rate of change, the limiter 32 g does not apply the limitingtask to the target attenuation-coefficient ξ_(tag), thus outputting thetarget attenuation-coefficient ξ_(tag) as it is.

This configuration also more efficiently balances between theimprovement of suppressing vibrations of the drivetrain of the vehicleVEH and the improvement of the driver's drivability of the vehicle VEH.

The degree of the Laplace operator s included in each of thedenominator, i.e. the modeled transfer characteristics Gpm(s), and thenumerator, i.e. the target transfer characteristics Gr(s), of theequation of the filter transfer characteristics I(s) according to eachembodiment is set to 2, but can be set to 3 or more.

The target attenuation-coefficient setter 32 c of the first embodimentcan set the target attenuation-coefficient ξ_(tag) when the limitedattenuation parameter Attr becomes its maximum value to a value greaterthan 1. The target attenuation-coefficient setter 32 e of the secondembodiment can set the target attenuation-coefficient ξ_(tag) when thelimited attenuation parameter Attr becomes its minimum value to a valuegreater than 1.

The calculator 32 a of the second ECU 32C can adjust the attenuationparameter Atp such that a value of the attenuation parameter Atp for thefirst situation is smaller than a value of the attenuation parameter Atpfor a third situation. The first situation represents a situation whereeach of the target MG torque Tm* and the target engine torque Te* ismore than zero and the request torque Tall of the vehicle VEH1 istransiently increasing (see the period from time t11 to time t12 of FIG.8). The third situation represents a situation where the request torqueTall of the vehicle VEH1 is transiently decreasing.

The target attenuation-coefficient setter 32 c of the first embodimentcontinuously increases the target attenuation-coefficient ξ_(tag) withan increase of the limited attenuation parameter Attr, but the presentdisclosure is not limited thereto. Specifically, the targetattenuation-coefficient setter 32 c can increase the targetattenuation-coefficient ξ_(tag) in several stages, such as three stages,with an increase of the limited attenuation parameter Attr. Similarly,the target attenuation-coefficient setter 32 e can decrease the targetattenuation-coefficient ξ_(tag) in several stages, such as three stages,with an increase of the limited attenuation parameter Attr.

The filter processor 32 d can be installed in the first ECU 30.

The vehicle plant model for the modeled transfer characteristics Gpm(s)and the target transfer characteristics Gr(s) has output torque Tds ofthe drive shaft 16 as its output, but the present disclosure is notlimited thereto. Specifically, a vehicle plant model having a rotationalspeed or a twisting angle θ of the drive shaft 16 as its output can beused as the vehicle plant model for the modeled transfer characteristicsGpm(s) and the target transfer characteristics Gr(s).

While illustrative embodiments of the present disclosure have beendescribed herein, the present disclosure is not limited to theembodiments described herein, but includes any and all embodimentshaving modifications, omissions, combinations (e.g., of aspects acrossvarious embodiments), adaptations and/or alternations as would beappreciated by those in the art based on the present disclosure. Thelimitations in the claims are to be interpreted broadly based on thelanguage employed in the claims and not limited to examples described inthe present specification or during the prosecution of the application,which examples are to be construed as non-exclusive.

What is claimed is:
 1. A control apparatus for a rotary electric machineof a vehicle, the vehicle being equipped with a drivetrain fortransmitting power output from the rotary electric machine to drivingwheels, the control apparatus comprising: a filter processor thatfilters target torque for the rotary electric machine to suppress avibrational frequency component of the drivetrain using a filter havinga frequency transfer characteristic; a controller that performs drivecontrol of the rotary electric machine according to the filtered targettorque; a parameter calculator that calculates, according to a runningcondition of the vehicle, a parameter associated with a request valuefor responsivity of output torque of the rotary electric machine withrespect to the target torque; a variable setter that variably sets thefrequency transfer characteristic of the filter to decrease a degree ofattenuation of the vibrational frequency component with an increase ofthe request value for responsivity of the actual output torque; and alimiter that limits a rate of change of the degree of attenuation tosuppress vibrations of the drivetrain.
 2. The control apparatusaccording to claim 1, wherein: the limiter comprises a gradual changerthat performs a gradual change task to gradually change the degree ofattenuation.
 3. The control apparatus according to claim 1, wherein: thedrivetrain includes a drive shaft coupling between the rotary electricmachine and the driving wheels; and the filter processor is configuredto apply, to the target torque, a filtering process based on the filterhaving the frequency transfer characteristic, the frequency transfercharacteristic being represented as a fractional expression of a targettransfer characteristic over a modeled transfer characteristic, themodeled transfer characteristic comprising a frequency transfercharacteristic of a plant model of the vehicle, the plant model havingthe output torque of the rotary electric machine as an input thereof,the plant model having, as an output thereof, an output parameterindicative of any one of output torque to the driving wheels, arotational speed of the drive shaft, and a twisting angle of the driveshaft, the target transfer characteristic comprising a target frequencytransfer characteristic of the plant model, each of the modeled transfercharacteristic and the target transfer characteristic including an N-thorder lag element where N is an integer equal to or more than
 2. 4. Thecontrol apparatus according to claim 3, wherein: the N-th order lagelement included in the target transfer characteristic has a termincluding an attenuation coefficient; and the variable setter isconfigured to variably set the attenuation coefficient to increase theattenuation coefficient with an increase of the request value forresponsivity of the actual output torque.
 5. The control apparatusaccording to claim 4, wherein: the variable setter is configured to: setthe attenuation coefficient to a first value that causes the frequencytransfer characteristic to be 1 when the request value of for theresponsivity of the output torque becomes minimum; and set theattenuation coefficient to a second value equal to or more than 1 whenthe request value of for the responsivity of the output torque becomesmaximum.
 6. The control apparatus according to claim 3, wherein: theN-th order lag element included in the modeled transfer characteristichas a term including an attenuation coefficient; and the variable setteris configured to variably set the attenuation coefficient to decreasethe attenuation coefficient with an increase of the request value forresponsivity of the actual output torque.
 7. The control apparatusaccording to claim 6, wherein: the variable setter is configured to: setthe attenuation coefficient to a first value equal to or more than 1when the request value of for the responsivity of the output torquebecomes minimum; and set the attenuation coefficient to a second valuethat causes the frequency transfer characteristic to be 1 when therequest value of for the responsivity of the output torque becomesmaximum.
 8. The control apparatus according to claim 2, wherein: thegradual changer is configured to perform, as the gradual change task, atask to gradually change a rate of change of the parameter calculated bythe parameter calculator.
 9. The control apparatus according to claim 4,wherein: the gradual changer is configured to perform, as the gradualchange task, a task to gradually change a rate of change of theattenuation coefficient.
 10. The control apparatus according to claim 1,wherein: the drivetrain is capable of transferring the power output fromthe rotary electric machine and power output from an internal combustionengine installed in the vehicle to the driving wheels; and the variablesetter is configured to variably set the frequency transfercharacteristic of the filter such that the degree of attenuation of thevibrational frequency component for a first situation is greater thanthe degree of attenuation of the vibrational frequency component for asecond situation, the first situation being a situation where the poweroutput from the rotary electric machine and power output from the engineare being transferred to the driving wheels and the sum of the targettorque for the rotary electric machine and second target torque for theinternal combustion engine is increasing, the second situation being atleast one of: a situation where the sum of the target torque for therotary electric machine and second target torque for the internalcombustion engine is in a steady state, and another situation where thesum of the target torque for the rotary electric machine and secondtarget torque for the internal combustion engine is decreasing.